Norovirus Infection

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

Mary D. Nettleman, MD, MS, MACP

Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.

There is no specific treatment for norovirus, but it
is important that infected people stay well hydrated. Fluids containing sugar
and electrolytes should be encouraged. Intravenous fluids may be needed if the
person cannot maintain an adequate oral intake of fluids.

Complications are usually
related to the degree of dehydration. Young children and the elderly are at
special risk for dehydration.

Because the disease is highly contagious, it is
important for caretakers to clean their hands whenever they come into contact
with the ill person or their environment.

The risk of food-borne outbreaks or
outbreaks within hospitals or nursing homes may be minimized by following
established standards that include hand hygiene.

What is a norovirus?

A norovirus is a small virus that contains RNA and is surrounded by a protein coating. By sequencing the RNA, scientists have discovered that there are many different types of norovirus. Originally, strains were named based on the city in which they were first identified. Thus, one common strain used to be called Norwalk virus. Based on genetic typing, we now know that there are at least 25 different strains of norovirus that affect humans. The RNA genome in noroviruses easily mutates to produce new norovirus types.

Norovirus infection is the most common cause of gastroenteritis outbreaks in the U.S. Although some people call this the "stomach flu," norovirus is not related to the influenza virus. According to statistics from the CDC, there are 21 million cases of norovirus infection annually in the U.S., of which one-quarter are related to food-borne outbreaks. Outbreaks occur throughout the year but are more common in the winter months. There is no specific treatment for norovirus. Fortunately, the disease is self-limited and simple supportive measures are sufficient to care for most people unless they become dehydrated. Outbreaks can occur almost anywhere in the world. In 2012, a new strain named GII.4 Sydney was identified. Since the first outbreak, the virus was quickly detected in New Zealand, France, and the U.S. It has caused about half of the norovirus infections detected in 2012-2013 in the U.S. A new outbreak of norovirus occurred at Yellowstone National Park, causing illness in about 200 visitors and camp employees in June 2013.